Touchless biometric recognition

ABSTRACT

1.  Touchless biometric recognition  
       2.1  The invention is underlied by the problem to specify a method of the type initially mentioned, with which an improved touchless biometric recognition is possible cheaply.  
       2.2  According to the invention, the problem is solved by mutually carrying out the observing, checking and/or correcting using the imaging facilities respectively and thereby acquiring position, attitude and degree of rotation.  
       2.3  The invention relates to a method for touchless recognition of biometric attributes of a body part, in particular of finger lines, comprising optical imaging from different points of view by several imaging facilities, observing and/or checking the position and/or the attitude of the body part to be recognized and/or correcting the images of the imaging facilities regarding the position and/or the attitude, wherein the shape of the body part is used.

The invention relates to a method for touchless recognition of biometricattributes of a body part, in particular of finger lines, comprisingoptical imaging from different points of view by several imagingfacilities, observing and/or checking the position and/or the attitudeof the body part to be recognized and/or correcting the images of theimaging facilities regarding the position and/or the attitude, whereinthe shape of the body part is used.

In manifold applications, security systems are applied to refuse accessto certain areas to unauthorized persons. Such areas are, for example,cash terminals, laboratory rooms to be kept secret and the like. Thesesystems mainly use facilities for recognition of fingerprints and faces.

There are substantial attempts to overcome these systems. To increasethe security, additional means are used, with which it is verified if itis the matter of a vital object.

In German Patent Document No. DE 101 23 561 A1, a method for identifyingpersons by means of biometric attributes of the finger tip is described,wherein both the shape of the finger tip and the fingerprint structurescontained on the bottom side of the finger, including their spatialposition and orientation on the finger tip, are detected as personalparameters by using images from different points of view by severalcameras to create a three-dimensional profile of the finger tip and itsdermal ridge structure. Thereby, the position and the rotation of thefinger can be determined by means of an additional camera in front ofthe finger tip in order to ask the user for a correction of the positionor to enhance the recognition analysis by the additional information ofthe degree of rotation of the finger.

In this method, the need of an additional camera for checking theposition is disadvantageous, because the imaging facilities are the mostexpensive parts of an optical recognition apparatus.

The invention is underlied by the problem to specify a method of thetype initially mentioned, with which an improved touchless biometricrecognition is possible cheaply.

According to the invention, the problem is solved by a method comprisingthe attributes given in claim 1.

Advantageous embodiments are given in the dependent claims.

The advantage of the method according to the invention is that only aleast possible number of imaging facilities is needed for the imagingfrom different directions, which fulfill two tasks at once and aretherefore exploited more efficiently.

An improved recognition is possible by using the finger image or thefinger model respectively across several phalanxes.

By measuring the respectively imaged nail surface, a simple and fastmeasurement of the degree of rotation of the finger is possible.

In the following, the invention is further explained consideringexamples of embodiments.

On this, it is shown by:

a schematic illustration of an arrangement for use with the methodaccording to the invention.

In FIG. 1, the two CCD cameras 2.1 and 2.2 exhibit an angle of 90° withrespect to each other and are located in the planes separated by theangles

and φ in a coordinate system x-y-z while taking images of the object 1.

In a recognition attempt, both cameras are taking images repeatedlyuntil both cameras determine a finger position acceptable for the othercamera respectively. This condition can be satisfied either for bothcameras simultaneously or temporally one after the other.

The same statement is valid for arrangements with more than two cameras.Then, the acceptances can be checked either pairwise or for a certaincamera by a group or all of the other cameras respectively.

Two-dimensional images from certain points of view or three-dimensionalmodels from the measurement data can be used as a reference and as arepresentation of the measurement data.

From the attitude, i.e., position, bending, degree of rotation, of thefinger, a calculational transformation of the images to a finger in a“normal attitude” is possible, i.e., for example, in elongated attitudewithout twist, which is preferably also present in the reference imagesand reference models.

Thereby, the attributes of the finger's phalanxes and of the fingernail, i.e. thickness, width, length, are preferably also used inaddition to the finger lines.

The degree of rotation of the finger can be calculated very easily fromthe nail surface respectively visible in the images.

The range of acceptance is clearly enhanced by the transformation to a“normal attitude”, whereby the procedure is carried out essentiallyfaster.

On the other hand, a feedback to the user can be given as long as adeviation of the position and/or attitude too large for a securerecognition is present, wherein the type and direction of the necessarychange in position or attitude can be announced or displayed.

Alternatively or additionally, a feedback can be given as soon as therecognition has been carried out successfully to inform the user aboutthe end of the procedure.

LIST OF REFERENCE NUMBERS

1 Object (finger)

2 Light detectors

3 First light detector in plane xy

4 Second light detector in plane zy

, φ Angles of the coordinate system

1-8. (canceled)
 9. A method for touchless recognition of at least onebiometric attribute of a body part comprising: capturing a plurality offirst optical images of the body part from a first point of view using afirst imaging device; capturing a plurality of second optical images ofthe body part from a second point of view using a second imaging device;monitoring and/or checking at least one of an attitude and a position ofthe body part; and correcting, where necessary, at least one of theplurality of first images and the plurality of second images withreference to the attitude or position using a shape of the body part,wherein at least one of the observing and correcting is performed usingan interaction between the first and second imaging devices so as todetermine a desired position, attitude and angle of rotation.
 10. Themethod as recited in claim 9, wherein the body part is a finger.
 11. Themethod as recited in claim 10, wherein the at least one biometricattribute includes a finger line pattern.
 12. The method as recited inclaim 9, further comprising creating a spatial, three-dimensionalprofile of the body part.
 13. The method as recited in claim 12 whereinthe three-dimensional profile includes a profile of a surface of thebody part.
 14. The method as recited in claim 9, wherein the imagesharpness is used as a criterion for reaching the desired position. 15.The method as recited in claim 9, further comprising applying atransformation of the at least one biometric attribute of the body partto a predetermined normal attitude and normal position of one of areference model and a reference image using measured values of theposition and/or the attitude
 16. The method as recited in claim 15,further comprising providing at least one of an optical and anacoustical feedback when a secure recognition is not possible despitethe calculational transformation.
 17. The method as recited in claim 16,wherein the feedback includes an indication of a type and direction of achange of attitude and/or position required for a secure recognition.18. The method as recited in claim 11, wherein the finger and its shapeare imaged and processed from the tip of the finger to at least beyondthe adjacent joint and wherein at least one angle of the joint is usedfor the observing, the checking and/or the correcting of the images. 19.The method as recited in claim 11, further comprising using thefingernail surface visible from the different points of view fordetermining the degree of rotation.